Polyethylene pipes are universal due to their excellent material characteristics. The pipe PND is increasingly used in everyday life. Installation can be done with your own hands, if everything is done according to the rules. This does not require special qualifications.
Material characteristics
The high demand for HDPE pipes is caused by the high quality of the material:
- temperature range - from -50 0 to +60 0 ;
- resistance to acidic and alkaline environments;
- high elasticity and strength;
- low thermal conductivity;
- polyethylene is not a conductor of electric current.
Pipe application
In the house or in the country from HDPE pipes are made:
- sewage and drainage;
- water pipes;
- gas supply to the house;
- cable channel for electrical wiring.
Pipe selection
For water supply with drinking water, pipes with a diameter of not more than 60 mm with a wall thickness of 4 mm are purchased. They must be designed for a working fluid pressure in the system of at least 1 MPa. The advantage is the absence of corrosion and taste of the metal in the water. If you want to equip a hot water supply, you need to know that at a temperature of 80 0 C the polyethylene softens, and with its further increase it begins to melt. In this regard, you should choose a brand not lower than PE80. For hot water, pipes can also be labeled PE-RT or PN20, they can withstand heat up to 110 0 C. For domestic conditions this is quite enough.
Distinguish between pipes for water supply and non-pressure pipes. For normal operating conditions of a water supply system, bays of 25 m in length with a wall thickness of at least 2 mm are taken. If the main line works under good pressure and has a diameter of more than 25 mm, then an inch pipe is taken as a branch. In any case, the branch must be of a smaller section than the general water supply.
Methods for connecting HDPE pipes
Before installation, you should choose a connection method, which can be as follows:
- One-piece - electrofusion or butt welding. The connection is the same strength as the pipe itself.
- The demountable method is a bell-shaped, compression and flange connection. Such piping systems are easy to assemble and dismantle; repairs or installation can be made in hard-to-reach places. Connections are made using fittings.
The connection method is selected depending on the following factors:
- pipe diameters;
- type of operation: pressureless, pressure head, cable laying;
- the use of fittings from different materials and with different diameters;
- site availability;
- the availability of welding equipment.
The most durable are welded and flange joints. The threaded sleeve with seal is unstable to stress. Installation of HDPE pipes for water pipes with compression fittings is usually done in personal plots for plant irrigation systems.
The weakest connections are bell-shaped. They are used only in pressure-free pipelines, with the exception of cases when the connection is made welded.
Compression fittings for HDPE pipes: installation
For HDPE pipes, mainly plastic fittings are used, but there are also more durable options from steel, cast iron, copper and brass. They differ in design and can be welded, threaded, with a press connection. For plastic pipes, compression fittings are mainly used, where the fixation is made by a clamping split ring made of hard plastic with notches, and sealing by tightening the sealing rings.
Like other connecting devices, compression fittings are of several types:
- coupling - for connecting pipes of equal diameter and direction;
- transition - for fastening the ends of pipes whose diameters are different (a metal-polyethylene transition is possible);
- bend, angle - rotate the structure by 45-120 0 ;
- tee, cross - for creating branches;
- nipple - a device for connecting a pipe to a hose;
- plug - for sealing pipe ends.
Before laying the water supply system, first of all, you need to draw a diagram of it with all fittings and valves. An unfolded pipe tends to twist, so it is fixed with clamps or pressed in a straightened state for 2 days.
If an HDPE pipe is selected for installation, installation is often done with compression fittings.
- The pipe is cut to the desired size with a special tool. You can use a conventional hacksaw for metal, but the end is made even and cleared of burrs.
- The hole is leveled by the calibrator, since its oval shape is unacceptable. At the end, an external chamfer is made.
- The fitting body is neatly connected to the pipe so as not to damage the rubber seals. Landing will be easier if you moisten the junction with water.
- The nut is tightened with hands. A key can be used to provide the required joint density.
- For the second pipe, the procedure is repeated.
It is convenient to use connections with compression fittings when installing HDPE pipes in the country. The system is easy to assemble in the spring at the site and dismantled in the fall.
Pluggable joints in hard to reach places are not made. It is convenient to use electric couplings with a built-in heater. The fitting connects 2 pipes, after which its heating is turned on and welding takes place with the formation of an integral unit. The price of the device is high, but the method is effective and often used.
Despite the possibility of dismantling in the compression fittings, the rubber gaskets should be replaced during reinstallation. This will ensure high reliability of the design.
Flange connections
When installing the HDPE pipe, installation for a diameter of more than 40 mm is preferably done using metal flanges. To do this, the edges of the pipes are cut with a pipe cutter at a right angle according to the finished marking. Then, polyethylene bushings with sides are welded to them, and metal flanges are mounted on them. Another way is to mount a compression flange on the pipe to fix a smooth polymer joint. Then, a regular flange is installed, which is fastened with studs and bolts with a similar part mounted on the end of the steel pipe.
Flange connection allows connecting valves, regulators, gate valves and pipes to each other.
Welded joints
Just like metal products, an HDPE pipe can be welded. Do-it-yourself installation is done using special equipment with electric heating of the joints.
- The joints are cleaned and welding equipment is being prepared.
- The welding parameters are set.
- The pipes are fixed in the clamps of the welding machine and centered. The ends are machined.
- Between the pipes, heaters are installed, with which the edges are melted.
- The ends come under pressure, which is maintained until it cools.
- Pipes are removed from the clamps.
The cost of installing HDPE pipes by welding depends on the diameter, but up to 63 mm the price is usually the same and is about 200 rubles. per joint.
When using an electric coupling, the installation costs are the same as for butt welding, but its price is higher. As a result, the cost is greater.
Hydraulic test
The operability of the collected water supply is checked by filling it with water for 2 hours. Then the system is pressurized and maintained for 30 minutes. The pipeline is inspected for leaks.
During operation, the state of the system is constantly monitored. With proper assembly, it will function for a long time.
Errors in the installation of HDPE pipes
- It is important to consider the linear expansion of the pipes from the action of temperature. If you forget about it, inside the pipes the voltage exceeds the norm, which reduces their life.
- Too much distance between the fasteners causes the pipeline to sag, which leads to its premature failure.
- Pipes are cemented only with insulation.
- To prevent condensation from forming on the surface, the pipelines for the supply of warm or cold water are insulated.
- During installation, the fitting is disassembled so that the pipes go all the way in. If the nut is not completely unscrewed, and then with effort to push the pipe into the connector, it may not enter deep enough. When installing HDPE pipes with your own hands in the country for an irrigation system, leaks are not so dangerous, but this is unacceptable for home water supply. Regardless of the consequences, in both cases it is necessary to create a tight connection.
- Excessive tightening of the adapters leads to their destruction or slipping out of the gaskets from the installation sites.
Conclusion
When installing the HDPE pipe, installation is done mainly by welding or compression fittings. Subject to the installation rules, the joints will be airtight and durable for many years.